What matters to Jackson is providing the Bills' sputtering offense a sense of identity now that he has reclaimed the starting job he had in taking over for Lynch midway through last season.

"That's the business side of it, that's what they handle upstairs," Jackson said before practice Wednesday, one day after Lynch was traded to the Seahawks in exchange for draft picks. "All we can do is come out here on the field and play with the guys we have. We have to focus on going out and winning football games."

And that has been the problem for the winless Bills, who are going through another round of upheaval while preparing to host the Jacksonville Jaguars (2-2) on Sunday.

Last week, Buffalo shuffled quarterbacks after cutting former starter Trent Edwards, who has since signed with Jacksonville and will serve as the team's backup this weekend. This week, its running backs, as the Bills came to the conclusion that three is, in fact, a crowd.

Lynch's departure frees up more carries for Jackson and rookie first-round pick C.J. Spiller, who has yet to provide the spark he showed in scoring three touchdowns this preseason.

The Bills also promoted rookie running back Andre Anderson from the practice squad Wednesday. He had 2,009 yards and 17 touchdowns in his career at Tulane.

In his first opportunity to discuss the trade, Bills coach Chan Gailey wouldn't provide details into the timing of the move even though Lynch had first asked to be dealt well before the Bills drafted Spiller.

"I don't get into sooner or later, there's a lot of things that go into decisions like this," Gailey said. "You're trying to do what's best for your team. And it worked out that a trade was made, and we're fortunate we have two good players that can carry the load for us the rest of the way."

Gailey said he's leaning on Jackson because, as a fourth-year pro, he has more experience. And he intends to have Spiller more involved. Spiller has scored a touchdown receiving and another on a kickoff return, but he has just 49 yards on 14 carries.

Lynch had received the bulk of the work in starting the past three games, and he led the Bills with 37 carries -- three more than Jackson and Spiller had combined -- for 164 yards. That left Jackson and Spiller splitting limited playing time because Buffalo's offense was either having difficulty sustaining drives or forced to play catch-up by going primarily with a passing attack.

Not much has worked on an offense that has failed to generate 230 yards in three of its four games and is averaging 13.5 first downs.

The Bills all but bottomed out in a 38-14 loss to the New York Jets last weekend. It was a game in which quarterback Ryan Fitzpatrick led the team with 74 rushing yards, and Buffalo went 0 of 10 in third-down conversions and finished with 19:31 in time of possession.

Enter Jackson, who had a breakout season last year in finishing with a team-leading and career-best 1,062 rushing yards.

Jackson learned of his promotion upon arriving for team meetings Wednesday and shortly after he wished Lynch well with his new team during a phone conversation.

"Now it's my time to stand up here and try to make plays," Jackson said. "It's going to be a challenge. It always is, but it's a challenge I'm looking forward to."

The trade didn't catch Jackson by surprise because he said Lynch had kept him up to date on the progress of talks over the past few weeks.

Spiller, selected ninth overall out of Clemson, was surprised by the move, saying he believe a three-back rotation had a chance to work. However, Spiller acknowledged he's having difficulty finding his niche.

"I'm still unsure what my role is," he said. "It's kind of disappointing that you don't really know. But at the same time, you know what you can bring to this team. I stay encouraged by that. So you just wait your turn and try to help the team any way you can."

Fitzpatrick wasn't surprised by the trade, given how Buffalo's offense has sputtered and the team is winless.

"Well, there's never a dull moment in the NFL, especially when you're losing," Fitzpatrick said. "It's just one of those things we had talked about, crowded backfield and trying to get everybody touches. Hopefully, it works out for Marshawn, and hopefully, it works out well for us."

Notes: LB Andra Davis returned to practice Wednesday and hopes to play this weekend despite revealing he has a shoulder injury that likely will require surgery. Davis said he has limited movement in his shoulder -- he didn't say which one -- but it shouldn't prevent him from playing because there's little chance of him doing further damage. ... DE Marcus Stroud returned to practice after missing last week's game with a left ankle injury. Stroud said he expects to play this weekend. ... Safety Bryan Scott (knee), LB Keith Ellison (knee), LB Arthur Moats (elbow) and CB Ashton Youboty (hamstring) didn't practice. Starting CB Terrence McGee already has been ruled out after having minor knee surgery last weekend. ... TE Shawn Nelson returned to practice after serving a four-game suspension for violating the NFL's substance-abuse policy. ... The Bills announced they have released TE Joe Klopfenstein from injured reserve and filled Anderson's practice-squad spot by signing DE Ra'Shon Harris, who appeared in two games with the Carolina Panthers last season and was released by the Pittsburgh Steelers this past summer.